Colorectal adenomas are well-documented precursors of colorectal cancer, the third most common cause of cancer mortality in the world. Patients who have a prior history of adenomas are at an increased risk of developing multiple sequential adenomas. Studies addressing risk factors for sequential adenoma formation, however, are extremely limited, largely due to the difficulty and high cost of conducting such investigations. in 1977-78, 2,815 colorectal polyp patients were identified in a mass screening in China. These patients were followed up using a rectoscope at years two, four, and six, and with a flexible 60 cm sigmoidoscope at years 10 and 15 after the initial screening. All medical records, questionnaires, and tissue blocks and slides of the polyps have been maintained in storage, but not yet computerized. This cohort provides the opportunity to assess in a cost-effective fashion risk factors for multiple sequential adenomas. To test the feasibility of conducting a longitudinal study within this polyp-screening population, a small scale pilot study will be needed. In this pilot study, we will establish a computerized data base for all study subjects; verify polyp diagnosis by reviewing all pathology slides using standardized criteria; pilot-test a lifestyle and family history questionnaire and procedures for blood collection and processing among 50 subjects randomly selected from the cohort. In addition, we will assess the value of pathologic features of polyps for predicting risk of subsequent polyp formation. The information obtained from this pilot study is essential to properly plan a more definitive full-scale longitudinal study.